CN102196111A - Short-wave two-path modulator-demodulator - Google Patents

Abstract

The invention discloses a two-way short-wave modem, which includes a two-way modulator and a two-way demodulator. Among the two-way modulators, one of the two-way modulators includes a sequentially connected convolutional code unit, a first waveform generating unit, a first A PSK modulation unit and a first waveform shaping unit; the other way includes a sequentially connected data modulation unit, a second waveform generating unit, a second PSK modulation unit and a second waveform shaping unit; in the two-way demodulator, one way includes The sequentially connected low-pass filter unit, the first interference suppression unit, the first time-domain equalization unit, the first PSK demodulation unit, and the first convolutional decoding unit; the other path includes a sequentially connected band-pass filter unit, the first Two interference suppression units, a second time-domain equalization unit, a second PSK demodulation unit, and a second convolutional decoding unit. Speed increase: Under the condition of certain channel quality, the communication data transmission rate is doubled. The performance of the short-wave two-way modem of the invention is improved, the compatibility is good, the functions are various, and the application is wide.

Description

A Shortwave Two-way Modem

technical field

The invention relates to a wireless data communication technology, which is mainly applied to a short-wave digital communication station, in particular to a short-wave two-way modem.

Background technique

The existing military and civilian short-wave digital communication stations mainly transmit data within the audio frequency bandwidth. In terms of transmission rate and transmission quality, due to the limitation of 3k audio bandwidth, it is increasingly unable to meet the needs of applications, especially the transmission needs of large amounts of data such as image and video transmission.

Contents of the invention

The technical problem to be solved by the invention is to provide a short-wave two-way modem for the deficiencies of the prior art. Adopt the following technical solutions:

A shortwave two-way modem that uses two parallel channels for data transmission.

In the short-wave two-way modem, the two-way parallel channels include two-way modulators and two-way demodulators, and one of the two-way modulators includes sequentially connected convolutional code units and first waveform generation units , the first PSK modulation unit and the first waveform shaping unit; the other road includes a sequentially connected data modulation unit, a second waveform generation unit, a second PSK modulation unit and a second waveform shaping unit; in the two-way demodulator , one path includes sequentially connected low-pass filtering unit, first interference suppression unit, first time-domain equalization unit, first PSK demodulation unit, first convolutional decoding unit; the other path includes sequentially connected bandpass filtering unit unit, a second interference suppression unit, a second time-domain equalization unit, a second PSK demodulation unit, and a second convolutional decoding unit.

The present invention mainly has the following beneficial effects:

Speed increase: Under the condition of certain channel quality, the communication data transmission rate is doubled.

Performance improvement: In the case of the same data transmission rate, the anti-interference performance of data transmission is doubled.

Compatibility: Each channel adopts the data transmission system of active radio stations, which can realize intercommunication with the data transmission of active radio stations.

Diversified functions: The two channels separately modulate and demodulate the data, and the transmission capabilities of the two channels can be used comprehensively, or the two channels can be used separately, such as to realize the simultaneous transmission of digital voice.

Wide range of applications: suitable for various short-wave radio stations at home and abroad.

Improved performance: By improving the communication performance of a single channel, the performance of a two-way modem can be doubled.

Description of drawings

Fig. 1 is a sending flowchart of the sending end of the present invention;

Fig. 2 is the receiving process of the receiving end of the present invention;

Fig. 3 is a model diagram of the XD-D12V shortwave radio station of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments.

Example 1

Two-way modems use two parallel channels for data transmission.

The total channel bandwidth is 7kHz, which is divided into two adjacent 3kHz channels, and a guard interval of 600Hz is reserved between the two channels.

The bandwidth of each channel is 3kHz, and the data transmission system of the "Fifteen" series of short-wave radio stations is adopted. Transmission of 75, 150, 300, 600, 1200 and 2400bps data respectively, the total rate reaches 150, 300, 600, 1200, 2400 and 4800bps.

According to the sampling theorem, the baseband sampling rate of the two-way modem is 19.2kbps, and its Nyquist frequency is 9.6kbps.

The baseband waveform is shaped using a square root raised cosine shaping filter.

The baseband signal is separated by a low-pass filter and a band-pass filter. The passband of the low-pass filter is 0Hz to 3300Hz, and the passband of the bandpass filter is 3900Hz to 6900Hz.

The data to be sent is allocated to two channels by using the data splitting protocol for modulation respectively. After the two channels of the receiver demodulate the data, the data is restored according to the data fusion protocol.

Example 2

The shortwave two-way modem includes two-way modulators and two-way demodulators; one of the two-way modulators includes a sequentially connected convolutional code unit, a first waveform generation unit, a first PSK modulation unit and a first Waveform shaping unit; the other road includes a sequentially connected data modulation unit, a second waveform generating unit, a second PSK modulation unit and a second waveform shaping unit; in the two-way demodulator, one road includes a sequentially connected low-pass Filtering unit, first interference suppression unit, first time domain equalization unit, first PSK demodulation unit, first convolutional decoding unit; the other path includes sequentially connected bandpass filter unit, second interference suppression unit, first Two time-domain equalization units, a second PSK demodulation unit, and a second convolutional decoding unit.

At the sending end, as shown in Figure 1, the data to be sent is split in the data splitting unit according to the data splitting protocol to form two channels of data, which are respectively entered into two channels of modulators for modulation: the data is coded and interleaved by the convolutional coding unit , the output coded bits are transmitted on their respective channels. The transmission process is as follows: the synchronization head first passes through the first waveform generation unit and the second waveform generation unit to generate a synchronization code; the coded bits enter the first waveform generation unit and the second waveform generation unit, and are transferred between the first waveform generation unit and the second waveform generation unit After performing scrambling and inserting pilot symbols, it is output to the first PSK modulation unit and the second PSK modulation unit to perform PSK modulation uniformly. After PSK modulation, it is moved to the corresponding carrier frequency. The waveform shaping unit performs waveform shaping respectively. The shaped two-way baseband signals are aliased and then sent to the up-conversion unit for up-conversion, and then enter the radio frequency unit for transmission.

At the receiving end, as shown in Figure 2, the baseband signals generated by the IF data after passing through the down-conversion unit respectively enter two demodulators for demodulation processing: after being filtered by a 3k broadband low-pass filter and a band-pass filter, Then remove the carrier of this channel, after the first interference suppression unit and the second interference suppression unit complete the interference suppression, then carry out signal identification and synchronization, and perform the following operations in the data stage, first enter the first time domain equalization unit, the second time domain equalization unit, The domain equalization unit performs time domain equalization; then enters the first PSK demodulation unit and the second PSK demodulation unit for PSK demodulation; then enters the first convolutional decoding unit and the second convolutional decoding unit for convolutional decoding , and finally adjust the sequence of the demodulated data in the data integration unit according to the data restoration protocol.

As shown in Figure 3, it is a schematic diagram of the implementation of the two-way modem of the present invention on the short-wave radio station XD-D12V. According to the channel requirements of the XD-D12V short-wave radio station, the intermediate frequency carrier of the two-way modem is 20KHz, and the sampling rate is 614.4Kbps. The down-conversion DDC mixes and extracts the intermediate frequency signal to generate a baseband signal. The corresponding digital rate changes from 614.4Kbps to 19.2Kbps, and the total extraction rate is 32. The up-conversion DUC converts the 19.2Kbps baseband signal into an intermediate frequency signal through interpolation and frequency mixing. The corresponding digital rate changes from 19.2Kbps to 614.4Kbps, and the interpolation is 32 times.

After XD-D12V shortwave radio adopts two modems, the data transmission rate can be realized at 150, 300, 600, 1200, 2400 and 4800bps.

It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should belong to the protection scope of the appended claims of the present invention.

Claims (2)

1. a shortwave two-way modulator-demodulator is characterized in that, adopts the two-way parallel channel to carry out transfer of data.

2. shortwave two-way modulator-demodulator according to claim 1, it is characterized in that, described two-way parallel channel comprises two-way modulator and two-way demodulator, in the described two-way modulator, the one tunnel comprises convolution code unit, first wave generating unit, a PSK modulating unit and the first waveform shaping unit that connects in turn; Another road comprises data-modulated unit, second wave generating unit, the 2nd PSK modulating unit and the second waveform shaping unit that connects in turn; In the described two-way demodulator, the one tunnel comprises that the low-pass filter unit, first that connects in turn disturbs inhibition unit, the first time domain equalization unit, a PSK demodulating unit, the first convolution decoding unit; Another road comprises that the bandpass filtering unit, second that connects in turn disturbs inhibition unit, the second time domain equalization unit, the 2nd PSK demodulating unit, the second folding coding unit.

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